Vitreous bonded abrasive articles and methods of manufacture thereof

ABSTRACT

A method of forming a vitreous bond abrasive article is presented that includes receiving, by a manufacturing device having one or more processors, a digital object comprising data specifying a plurality of layers of a vitreous bond abrasive article precursor. The vitreous bond abrasive article precursor includes abrasive particles bonded together by a vitreous bond precursor material and an organic compound. The vitreous bond abrasive article precursor further comprises at least one of: at least one tortuous cooling channel extending at least partially through the vitreous bond abrasive article precursor or at least one arcuate cooling channel extending at least partially through the vitreous bond abrasive article precursor. The method also includes generating, with the manufacturing device by an additive manufacturing process, the vitreous bond abrasive article precursor based on the digital object.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/076,742, filed Aug. 9, 2018, which is a national stage filing under35 U.S.C. 371 of PCT/US2017/024882, filed Mar. 30, 2017, which claimsthe benefit of U.S. Application No. 62/315,044, filed Mar. 30, 2016, thedisclosures of which are incorporated by reference in their entiretyherein.

TECHNICAL FIELD

The present disclosure broadly relates to methods of making abrasivearticles having abrasive particles in a metallic bonding matrix or avitreous bonding matrix.

BACKGROUND

Traditionally, vitrified bond abrasive articles (e.g., abrasive wheels,abrasive segments, and whetstones) are made by compressing a blend ofabrasive particles (e.g., diamond, cubic boron nitride, alumina, orSiC), a vitreous bond precursor (e.g., glass frit, ceramic precursor) anoptional pore inducer (e.g., glass bubbles, naphthalene, crushed coconutor walnut shells, or acrylic glass or PMMA), and a temporary organicbinder in a liquid vehicle (e.g., aqueous solutions of phenolic resin,polyvinyl alcohol, urea-formaldehyde resin, or dextrin). The abrasiveparticles, vitreous bond precursor, and usually the pore inducer aretypically dry blended together. The temporary organic binder solution isthen added to wet out the grain mix. The blended mix is then placed in ahardened steel mold treated with a mold release. The filled mold is thencompressed in a press to form a molded green body. The green body thenis ejected from the mold, and subsequently heated until the temporaryorganic binder is burned out and the vitreous bond precursor isconverted into a vitreous bond matrix (also referred to in the art as“vitreous bond” and “vitreous binder”.

Traditionally, metal bond abrasive articles are made by mixing anabrasive grit, such as diamond, cubic boron nitride (cBN), or otherabrasive grains with a non-melting metal powder (e.g., tungsten,stainless steel, or others), a melting metal powder (e.g., bronze orcopper), or a combination thereof. Pore inducers, temporary binders andother additives may be added. The mixture is then introduced into a moldthat has been coated with a mold release agent. The filled mold is thencompressed in a press to form a molded green body. The green body thenis ejected from the mold and subsequently heated in a furnace at hightemperature to melt a portion of the metal composition, or it is infusedwith a molten metal. The heating is typically done in a suitablecontrolled atmosphere of inert or reducing gas (e.g., nitrogen, argon,hydrogen) or in a vacuum.

There are many disadvantages to these manufacturing approaches: eachabrasive article shape requires a special mold; the molds typically areexpensive and have a long lead time to make; any design change requiresthe manufacture of a new mold; there are limitations to the shapes thatcan be molded, complicated shapes with undercuts or internal structuressuch as cooling channels are generally not possible; molds wear out andhave a limited number of units that can be manufactured per mold; whilethe molds are filled with the abrasive mixture, separation of thecomponents can occur, leading to inhomogeneous abrasive components anddensity variation, which is easily visible and may cause performancevariations. Moreover, the processes are often manual and laborintensive.

In selective laser sintering, a layer of powder comprising a metalpowder and an abrasive grain is spread in a uniform layer in an inertatmosphere enclosure. In predetermined areas, the powder is heated by alaser beam to heat the metal powder to its sintering temperature. Adisadvantage of traditional laser sintering is that a high powered laseris required (e.g., in the range of 30-150 watts) and that the inertatmosphere needs to be maintained throughout the printing process.

SUMMARY

In a first aspect, the present disclosure provides a method of making avitreous bond abrasive article, the method including sequential steps.Step a) includes a subprocess including sequentially: i) depositing alayer of loose powder particles in a confined region; and ii)selectively applying heat via conduction or irradiation, to heat treatan area of the layer of loose powder particles. The loose powderparticles include vitreous bond precursor particles, abrasive particles,and organic compound particles. The layer of loose powder particles hassubstantially uniform thickness. Step b) includes independently carryingout step a) a plurality of times to generate an abrasive article preformcomprising the bonded powder particles and remaining loose powderparticles. In each step a), the loose powder particles are independentlyselected. Step c) includes separating substantially all of the remainingloose powder particles from the abrasive article preform; and step d)includes heating the abrasive article preform to provide the vitreousbond abrasive article comprising the abrasive particles retained in avitreous bond material.

In a second aspect, the present disclosure provides a vitreous bondabrasive article precursor including abrasive particles bonded togetherby a vitreous bond precursor material and an organic compound, whereinthe vitreous bond abrasive article precursor further includes at leastone of at least one tortuous cooling channel extending at leastpartially through the vitreous bond abrasive article precursor; or atleast one arcuate cooling channel extending at least partially throughthe vitreous bond abrasive article precursor.

In a third aspect, the present disclosure provides a method of making ametal bond abrasive article, the method comprising sequential steps.Step a) includes a subprocess including sequentially: i) depositing alayer of loose powder particles in a confined region; and ii)selectively applying heat via conduction or irradiation, to heat treatan area of the layer of loose powder particles. The loose powderparticles include higher melting metal particles, abrasive particles,and organic compound particles. The layer of loose powder particles hassubstantially uniform thickness. Step b) includes independently carryingout step a) a plurality of times to generate an abrasive article preformcomprising the bonded powder particles and remaining loose powderparticles. In each step a), the loose powder particles are independentlyselected. Step c) includes separating substantially all of the remainingloose powder particles from the abrasive article preform. Step d)includes infusing the abrasive article preform with a molten lowermelting metal, wherein at least some of the higher melting metalparticles do not completely melt when contacted by the molten lowermelting metal. Step e) includes solidifying the molten lower meltingmetal to provide the metal bond abrasive article.

In a fourth aspect, the present disclosure provides a method of making ametal bond abrasive article, the method including sequential steps. Stepa) includes a subprocess including sequentially: i) depositing a layerof loose powder particles in a confined region; and ii) selectivelyapplying heat via conduction or irradiation, to heat treat an area ofthe layer of loose powder particles. The loose powder particles includemetal particles, abrasive particles, and organic compound particles. Thelayer of loose powder particles has substantially uniform thickness.Step includes b) independently carrying out step a) a plurality of timesto generate an abrasive article preform comprising the bonded powderparticles and remaining loose powder particles, wherein the abrasivearticle preform has a predetermined shape. In each step a), the loosepowder particles are independently selected. Step c) includes separatingsubstantially all of the remaining loose powder particles from theabrasive article preform. Step d) includes heating the abrasive articlepreform to provide the metal bond abrasive article.

In a fifth aspect, the present disclosure provides a metal bond abrasivearticle precursor including metallic particles and abrasive particlesbonded together by an organic compound material, wherein the metal bondabrasive article precursor further includes at least one of: at leastone tortuous cooling channel extending at least partially through themetal bond abrasive article precursor; and at least one arcuate coolingchannel extending at least partially through the metal bond abrasivearticle precursor.

In a sixth aspect, the present disclosure provides a non-transitorymachine readable medium having data representing a three-dimensionalmodel of a vitreous bond abrasive article, when accessed by one or moreprocessors interfacing with a 3D printer, causes the 3D printer tocreate a vitreous bond abrasive article precursor of the vitreous bondabrasive article. The vitreous bond abrasive article precursor includesabrasive particles bonded together by a vitreous bond precursor materialand an organic compound. The vitreous bond abrasive article precursorfurther includes at least one of at least one tortuous cooling channelextending at least partially through the vitreous bond abrasive articleprecursor; or at least one arcuate cooling channel extending at leastpartially through the vitreous bond abrasive article precursor.

In a seventh aspect, the present disclosure provides a method includingretrieving, from a (e.g., non-transitory) machine readable medium, datarepresenting a 3D model of a vitreous bond abrasive article. A vitreousbond abrasive article precursor of the vitreous bond abrasive articlepreform includes abrasive particles bonded together by a vitreous bondprecursor material and an organic compound. The vitreous bond abrasivearticle precursor further includes at least one of at least one tortuouscooling channel extending at least partially through the vitreous bondabrasive article precursor; or at least one arcuate cooling channelextending at least partially through the vitreous bond abrasive articleprecursor. The method further includes executing, by one or moreprocessors, a 3D printing application interfacing with a manufacturingdevice using the data; and generating, by the manufacturing device, aphysical object of the vitreous bond abrasive article precursor.

In an eighth aspect, the present disclosure provides a method includingreceiving, by a manufacturing device having one or more processors, adigital object comprising data specifying a plurality of layers of avitreous bond abrasive article precursor. The vitreous bond abrasivearticle precursor includes abrasive particles bonded together by avitreous bond precursor material and an organic compound. The vitreousbond abrasive article precursor further includes at least one of atleast one tortuous cooling channel extending at least partially throughthe vitreous bond abrasive article precursor; or at least one arcuatecooling channel extending at least partially through the vitreous bondabrasive article precursor. The method further includes generating, withthe manufacturing device by an additive manufacturing process, thevitreous bond abrasive article precursor based on the digital object.

In a ninth aspect, the present disclosure provides a system including adisplay that displays a 3D model of a vitreous bond abrasive article;and one or more processors that, in response to the 3D model selected bya user, cause a 3D printer to create a physical object of a vitreousbond abrasive article precursor of the vitreous bond abrasive article.The vitreous bond abrasive article precursor includes abrasive particlesbonded together by a vitreous bond precursor material and an organiccompound. The vitreous bond abrasive article precursor further includesat least one of at least one tortuous cooling channel extending at leastpartially through the vitreous bond abrasive article precursor; or atleast one arcuate cooling channel extending at least partially throughthe vitreous bond abrasive article precursor.

In a tenth aspect, the present disclosure provides a non-transitorymachine readable medium having data representing a three-dimensionalmodel of a metal bond abrasive article, when accessed by one or moreprocessors interfacing with a 3D printer, causes the 3D printer tocreate the metal bond abrasive article precursor of the metal bondabrasive article. The metal bond abrasive article precursor includesmetallic particles and abrasive particles bonded together by an organiccompound material. The metal bond abrasive article precursor furtherincludes at least one of at least one tortuous cooling channel extendingat least partially through the metal bond abrasive article precursor;and at least one arcuate cooling channel extending at least partiallythrough the metal bond abrasive article precursor.

In an eleventh aspect, the present disclosure provides a methodincluding retrieving, from a non-transitory machine readable medium,data representing a 3D model of a metal bond abrasive article precursor.The metal bond abrasive article precursor includes metallic particlesand abrasive particles bonded together by an organic compound material.The metal bond abrasive article precursor further includes at least oneof at least one tortuous cooling channel extending at least partiallythrough the metal bond abrasive article precursor; and at least onearcuate cooling channel extending at least partially through the metalbond abrasive article precursor. The method further includes executing,by one or more processors, a 3D printing application interfacing with amanufacturing device using the data; and generating, by themanufacturing device, a physical object of the metal bond abrasivearticle precursor.

In a twelfth aspect, the present disclosure provides a method includingreceiving, by a manufacturing device having one or more processors, adigital object comprising data specifying a plurality of layers of ametal bond abrasive article precursor. The metal bond abrasive articleprecursor includes metallic particles and abrasive particles bondedtogether by an organic compound material. The metal bond abrasivearticle precursor further includes at least one of at least one tortuouscooling channel extending at least partially through the metal bondabrasive article precursor; and at least one arcuate cooling channelextending at least partially through the metal bond abrasive articleprecursor. The method further includes generating, with themanufacturing device by an additive manufacturing process, the metalbond abrasive article precursor based on the digital object.

In a thirteenth aspect, the present disclosure provides a systemincluding a display that displays a 3D model of a metal bond abrasivearticle; and one or more processors that, in response to the 3D modelselected by a user, cause a 3D printer to create a physical object of ametal bond abrasive article precursor of the metal bond abrasivearticle. The metal bond abrasive article precursor includes metallicparticles and abrasive particles bonded together by an organic compoundmaterial. The metal bond abrasive article precursor further includes atleast one of at least one tortuous cooling channel extending at leastpartially through the metal bond abrasive article precursor; and atleast one arcuate cooling channel extending at least partially throughthe metal bond abrasive article precursor.

Features and advantages of the present disclosure will be furtherunderstood upon consideration of the detailed description as well as theappended claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A is a schematic process flow diagram of a method of making avitreous bond or metal bond abrasive article according to the presentdisclosure.

FIG. 1B is a schematic cross-sectional side view of the third step ofthe process of FIG. 1A with a thermal print head heat source.

FIG. 1C is a schematic cross-sectional side view of the third step ofthe process of FIG. 1A with a heated tip heat source.

FIG. 1D is a schematic cross-sectional side view of the third step ofthe process of FIG. 1A with a laser heat source.

FIG. 2 is a schematic cross-sectional top view of an exemplary vitreousbond or metal bond abrasive wheel 200, preparable according to thepresent disclosure.

FIG. 3 is a schematic cross-sectional top view of an exemplary vitreousbond or metal bond abrasive wheel 300, preparable according to thepresent disclosure.

FIG. 4 is a schematic perspective view of an exemplary vitreous bond ormetal bond abrasive segment 400, preparable according to the presentdisclosure.

FIG. 5 is a schematic perspective view of a vitreous bond or metal bondabrasive wheel 500, preparable according to the present disclosure.

FIG. 6A is a schematic perspective view of a unitary structured abrasivedisc 600, preparable according to the present disclosure.

FIG. 6B is a schematic top view of unitary structured abrasive disc 600.

FIG. 7A is a schematic perspective view of a unitary structured abrasivedisc 700, preparable according to the present disclosure.

FIG. 7B is a schematic top view of unitary structured abrasive disc 700.

FIG. 8 is a schematic perspective view of rotary abrasive tool 800,preparable according to the present disclosure.

FIG. 9 is a schematic perspective view of an exemplary dental bur 900,preparable according to the present disclosure.

FIG. 10 is a schematic front view of an exemplary computing device 1000.

FIG. 11 is a block diagram of a generalized system 1150 for additivemanufacturing of a vitreous bond or metal bond abrasive article.

FIG. 12 is a block diagram of a generalized manufacturing process for avitreous bond or metal bond abrasive article.

FIG. 13 is a high-level flow chart of an exemplary vitreous bond ormetal bond abrasive article manufacturing process.

FIG. 14 is a high-level flow chart of an exemplary vitreous bond ormetal bond abrasive article additive manufacturing process.

Repeated use of reference characters in the specification and drawingsis intended to represent the same or analogous features or elements ofthe disclosure. It should be understood that numerous othermodifications and embodiments can be devised by those skilled in theart, which fall within the scope and spirit of the principles of thedisclosure. The figures may not be drawn to scale.

DETAILED DESCRIPTION

Methods of making vitreous bond abrasive articles and metal bondabrasive articles according to the present disclosure include a commonadditive subprocess. The subprocess comprises sequentially, preferablyconsecutively (although not required), carrying out at least threesteps. Advantageously, the methods involve selectively applying heat viaconduction or irradiation without requiring any high powered equipmentas the heat source and without the need for an inert atmosphere.

FIG. 1A schematically depicts an exemplary powder bed process 100 usedin making a vitreous bond abrasive article or a metal bond abrasivearticle.

In the first step, a layer 138 of loose powder particles 110 from powderchamber 120 a with movable piston 122 a is deposited in a confinedregion 140 in powder chamber 120 b with movable piston 122 b. The layer138 should be of substantially uniform thickness. For example, thethickness of the layer may vary less than 50 microns, preferably lessthan 30 microns, and more preferably less than 10 microns. The layersmay have any thickness up to about 1 millimeter, as long as heat canbind all the loose powder where it is applied. Preferably, the thicknessof the layer is from about 10 microns to about 500 microns, 10 micronsto about 250 microns, more preferably about 50 microns to about 250microns, and more preferably from about 100 microns to about 200microns.

The abrasive particles may comprise any abrasive particle used in theabrasives industry. Preferably, the abrasive particles have a Mohshardness of at least 4, preferably at least 5, more preferably at least6, more preferably at least 7, more preferably at least 8, morepreferably at least 8.5, and more preferably at least 9. In certainembodiments, the abrasive particles comprise superabrasive particles. Asused herein, the term “superabrasive” refers to any abrasive particlehaving a hardness greater than or equal to that of silicon carbide(e.g., silicon carbide, boron carbide, cubic boron nitride, anddiamond).

Specific examples of suitable abrasive materials include aluminum oxide(e.g., alpha alumina) materials (e.g., fused, heat-treated, ceramic,and/or sintered aluminum oxide materials), silicon carbide, titaniumdiboride, titanium nitride, boron carbide, tungsten carbide, titaniumcarbide, aluminum nitride, diamond, cubic boron nitride (CBN), garnet,fused alumina-zirconia, sol-gel derived abrasive particles, metal oxidessuch as cerium oxide, zirconium oxide, titanium oxide, and combinationsthereof. In certain embodiments, the abrasive particles comprise metaloxide ceramic particles. Examples of sol-gel derived abrasive particlescan be found in U.S. Pat. No. 4,314,827 (Leitheiser et al.), U.S. Pat.No. 4,623,364 (Cottringer et al.); U.S. Pat. No. 4,744,802 (Schwabel),U.S. Pat. No. 4,770,671 (Monroe et al.); and U.S. Pat. No. 4,881,951(Monroe et al.). Agglomerate abrasive particles that comprise finerabrasive particles in a vitreous bond matrix (e.g., as described in U.S.Pat. No. 6,551,366 (D'Souza et al.)) may also be used.

As noted above, the loose powder particles include organic compoundparticles, which were discovered to be capable of holding together theabrasive particles (as well as other types of particles present in theloose powder particles) upon the select application of heat. In manyembodiments, the organic compound particles have a melting point between50 degrees Celsius and 250 degrees Celsius, inclusive, such as between100 degrees Celsius to 180 degrees Celsius, inclusive. Stated anotherway, in certain embodiments, the organic compound particles have amelting point of at least 50 degrees Celsius, or at least 60, or atleast 70, or at least 80, or at least 90, or at least 100, or at least110, or at least 120, or at least 130 degrees Celsius; and a meltingpoint of up to 250 degrees Celsius, or up to 240, or up to 230, or up to220, or up to 210, or up to 200, or up to 190, or up to 180, or up to170, or up to 160 degrees Celsius.

The organic compound particles are not particularly limited, and areoptionally selected from waxes, sugars, dextrins, thermoplastics havinga melting point of no greater than 250 degrees Celsius, acrylates,methacrylates, and combinations thereof.

Suitable waxes include for example and without limitation, materials ofvegetable, animal, petroleum, and/or mineral derived origin.Representative waxes include carnauba wax, candelilla wax, oxidizedFischer-Tropsch wax, microcrystalline wax, lanolin, bayberry wax, palmkernel wax, mutton tallow wax, polyethylene wax, polyethylene copolymerwax, petroleum derived waxes, montan wax derivatives, polypropylene wax,oxidized polyethylene wax, and combinations thereof.

Suitable sugars include for example and without limitation, lactose,trehalose, glucose, sucrose, levulose, dextrose, and combinationsthereof.

Suitable dextrins include for example and without limitation,gamma-cyclodextrin, alpha-cyclodextrin, beta-cyclodextrin,glucosyl-alpha-cyclodextrin, maltosyl-alpha-cyclodextrin,glucosyl-beta-cyclodextrin, maltosyl-beta-cyclodextrin,2-hydroxy-beta-cyclodextrin, 2-hydroxypropyl-beta-cyclodextrin,2-hydroxypropyl-gamma-cyclodextrin, hydroxyethyl-beta-cyclodextrin,methyl-beta-cyclodextrin, sulfobutylether-alpha-cyclodextrin,sulfobutylether-beta-cyclodextrin, sulfobutylether-gamma-cyclodextrin,and combinations thereof.

Suitable thermoplastics include for example and without limitation,thermoplastics having a melting point of no greater than 250 degreesCelsius, such as polyethyleneterephthalate (PET), polylactic acid (PLA),polyvinyl chloride (PVC), polymethyl methacrylate (PMMA), polypropylene(PP), bisphenol-A polycarbonate (BPA-PC), polysulfone (PSF), polyetherimide (PEI), and combinations thereof.

Suitable acrylates and methacrylates include for example and withoutlimitation, urethane acrylates, epoxy acrylates, polyester acrylates,acrylated (meth)acrylics, polyether acrylates, acrylated polyolefins,and combinations thereof, or their methacrylate analogs.

The organic compound particles are typically present in an amount of 2.5weight percent to 30 weight percent of the loose powder particles,inclusive, such as 5 weight percent to 20 weight percent of the loosepowder particles, inclusive. Stated another way, in certain embodimentsthe organic compound particles are present in an amount of at least 2.5weight percent, or at least 3 weight percent, or at least 4 weightpercent, or at least 5 weight percent, or at least 7 weight percent, orat least 8 weight percent, or at least 10 weight percent, or at least 12weight percent of the loose powder particles; and up to 30 weightpercent, or up to 28 weight percent, or up to 25 weight percent, or upto 23 weight percent, or up to 20 weight percent, or up to 18 weightpercent of the loose powder particles. Typically, the average particlesize of the organic compound particles ranges from about 1 micrometer toabout 100 micrometers, preferably about 5 micrometers to about 50micrometers, and most preferably about 10 micrometers to about 30micrometers.

When forming a vitreous bond abrasive article, the loose powderparticles comprise vitreous bond precursor particles, abrasiveparticles, and organic compound particles. When forming a metal bondabrasive article, the loose powder particles comprise metal particles,abrasive particles, and organic compound particles. In certainembodiments of forming a metal bond abrasive article, the metalparticles comprise higher melting metal particles.

The vitreous bond precursor particles may comprise particles of anymaterial that can be thermally converted into a vitreous material.Examples include glass frit particles, ceramic particles, ceramicprecursor particles, and combinations thereof.

The vitreous bond which binds together the abrasive grain in accordancewith this disclosure can be of any suitable composition which is knownin the abrasives art. The vitreous bond phase, also variously known inthe art as a “ceramic bond”, “vitreous phase”, “vitreous matrix”, or“glass bond” (e.g., depending on the composition) may be produced fromone or more oxide (e.g., a metal oxide and/or boria) and/or at least onesilicate as frit (i.e., small particles), which upon being heated to ahigh temperature react to form an integral vitreous bond phase. Examplesinclude glass particles (e.g., recycled glass frit, water glass frit),silica frit (e.g., sol-gel silica frit), alumina trihydrate particles,alumina particles, zirconia particles, and combinations thereof.Suitable frits, their sources and compositions are well known in theart.

Abrasive articles are typically prepared by forming a green structurecomprised of abrasive grain, the vitreous bond precursor, an optionalpore former, and a temporary binder. The green structure is then fired.The vitreous bond phase is usually produced in the firing step of theprocess for producing the abrasive article of this disclosure. Typicalfiring temperatures are in the range of from 540° C. to 1700° C. (1000°F. to 3100° F.). It should be understood that the temperature selectedfor the firing step and the composition of the vitreous bond phase mustbe chosen so as to not have a detrimental effect on the physicalproperties and/or composition of abrasive particles contained in thevitreous bond abrasive article.

Useful glass frit particles may include any glass frit material knownfor use in vitreous bond abrasive articles. Examples include glass fritselected from the group consisting of silica glass frit, silicate glassfrit, borosilicate glass frit, and combinations thereof. In oneembodiment, a typical vitreous binding material contains about 70-90%SiO₂+B₂O₃, 1-20% alkali oxides, 1-20% alkaline earth oxides, and 1-20%transition metal oxides. In another embodiment, the vitreous bindingmaterial has a composition of about 82 wt % SiO₂+B₂O₃, 5% alkali metaloxide, 5% transition series metal oxide, 4% Al₂O₃, and 4% alkaline earthoxide. In another embodiment, a frit having about 20% B₂O₃, 60% silica,2% soda, and 4% magnesia may be utilized as the vitreous bindingmaterial. One of skill in the art will understand that the particularcomponents and the amounts of those components can be chosen in part toprovide particular properties of the final abrasive article formed fromthe composition.

The size of the glass frit can vary. For example, it may be the samesize as the abrasive particles, or different. Typically, the averageparticle size of the glass frit ranges from about 0.01 micrometer toabout 100 micrometers, preferably about 0.05 micrometer to about 50micrometers, and most preferably about 0.1 micrometer to about 25micrometers. The average particle size of the glass frit in relation tothe average particle size of the abrasive particles having a Mohshardness of at least about 4 can vary. Typically, the average particlesize of the glass frit is about 1 to about 200 percent of the averageparticle size of the abrasive, preferably about 10 to about 100 percent,and most preferably about 15 to about 50 percent.

Typically, the weight ratio of vitreous bond precursor particles toabrasive particles in the loose powder particles ranges from about 10:90to about 90:10. The shape of the vitreous bond precursor particles canalso vary. Typically, they are irregular in shape (e.g., crushed andoptionally graded), although this is not a requirement. For example,they may be spheroidal, cubic, or some other predetermined shape.

Preferably, the coefficient of thermal expansion of the vitreous bondprecursor particles is the same or substantially the same as that of theabrasive particles.

One preferred vitreous bond has an oxide-based mole percent (%)composition of SiO₂ 63.28; TiO₂ 0.32; Al₂O₃ 10.99; B₂O₃ 5.11; Fe₂O₃0.13; K₂O 3.81; Na₂O 4.20; Li₂O 4.98; CaO 3.88; MgO 3.04 and BaO 0.26.Firing of these ingredients is typically accomplished by raising thetemperature from room temperature to the desired sintering temperature(e.g., 1149° C. (2100° F.)), over a prolonged period of time (e.g.,about 25-26 hours), holding at the maximum temperature (e.g., forseveral hours), and then cooling the fired article to room temperatureover an extended period of time (e.g., 25-30 hours).

It is known in the art to use various additives in the making ofvitreous bonded abrasive articles both to assist in the making of theabrasive article and/or improve the performance of such articles. Suchconventional additives which may also be used in the practice of thisdisclosure include but are not limited to lubricants, fillers, poreinducers, and processing aids. Examples of lubricants include, graphite,sulfur, polytetrafluoroethylene and molybdenum disulfide. Examples ofpore inducers include glass bubbles and organic particles.Concentrations of the additives as are known in the art may be employedfor the intended purpose of the additive, for example. Preferably, theadditives have little or no adverse effect on abrasive particlesemployed in the practice of this disclosure.

The vitreous bond precursor particles may comprise ceramic particles. Insuch cases sintering and/or fusing of the ceramic particles forms thevitreous matrix. Any sinterable and/or fusible ceramic material may beused. Preferred ceramic materials include alumina, zirconia, andcombinations thereof. The inorganic vitreous bond precursor optionallyincludes a precursor of alpha alumina. In certain embodiments, theabrasive particles and the vitreous bond material have the same chemicalcomposition.

If desired, alpha-alumina ceramic particles may be modified with oxidesof metals such as magnesium, nickel, zinc, yttria, rare earth oxides,zirconia, hafnium, chromium, or the like. Alumina and zirconia abrasiveparticles may be made by a sol-gel process, for example, as disclosed inU.S. Pat. No. 4,314,827 (Leitheiser et al.); U.S. Pat. No. 4,518,397(Leitheiser et al.); U.S. Pat. No. 4,574,003 (Gerk); U.S. Pat. No.4,623,364 (Cottringer et al.); U.S. Pat. No. 4,744,802 (Schwabel); andU.S. Pat. No. 5,551,963 (Larmie).

The vitreous bond precursor particles may be present in an amount from10 to 40 volume percent of the combined volume of the vitreous bondprecursor particles and abrasive particles, preferably from 15 to 35volume percent of the abrasive composition.

In the case of the metal bond precursor particles, the optional highermelting metal particles may comprise any metal from group 2 through togroup 15 of the Periodic Table of the elements, for example. Alloys ofthese metals, and optionally with one or more elements (e.g., metalsand/or non-metals such as carbon, silicon, boron) in groups 1 and 15 ofthe Periodic Table, may also be used. Examples of suitable metalparticles include powders comprising magnesium, aluminum, iron,titanium, niobium, tungsten, chromium, tantalum, cobalt, nickel,vanadium, zirconium, molybdenum, palladium, platinum, copper, silver,gold, cadmium, tin, indium, tantalum, zinc, alloys of any of theforegoing, and combinations thereof.

Higher melting metal particles preferably having a melting point of atleast about 1100° C., and more preferably at least 1200° C., althoughlower melting metals may also be used. Examples include stainless steel(about 1360-1450° C.), nickel (1452° C.), steel (1371° C.), tungsten(3400° C.), chromium (1615° C.), Inconel (Ni+Cr+Fe, 1390-1425° C.), iron(1530° C.), manganese (1245-1260° C.), cobalt (1132° C.), molybdenum(2625° C.), Monel (Ni+Cu, 1300-1350° C.), niobium (2470° C.), titanium(1670° C.), vanadium (1900° C.), antimony (1167° C.), Nichrome (Ni+Cr,1400° C.), alloys of the foregoing (optionally also including one ormore of carbon, silicon, and boron), and combinations thereof.Combinations of two or more different higher melting metal particles mayalso be used.

The loose powder particles may optionally further comprise lower meltingmetal particles (e.g., braze particles). The lower melting metalparticles preferably have a maximum melting point that is at least 50°C. lower (preferably at least 75° C. lower, at least 100° C., or even atleast 150° C. lower) than the lowest melting point of the higher meltingmetal particles. As used herein, the term “melting point” includes alltemperatures in a melting temperature range of a material. Examples ofsuitable lower melting metal particles include particles of metals suchas aluminum (660° C.), indium (157° C.), brass (905-1083° C.), bronze(798-1083° C.), silver (961° C.), copper (1083° C.), gold (1064° C.),lead (327° C.), magnesium (671° C.), nickel (1452° C., if used inconjunction with higher melting point metals), zinc (419° C.), tin (232°C.), active metal brazes (e.g., InCuAg, TiCuAg, CuAg), alloys of theforegoing, and combinations thereof.

Typically, the weight ratio of high melting metal particles and/oroptional lower melting metal particles to the abrasive particles rangesfrom about 10:90 to about 90:10, although this is not a requirement.

The loose powder particles may optionally further comprise othercomponents such as, for example, pore inducers, fillers, and/or fluxingagent particles. Examples of pore inducers include glass bubbles andorganic particles. In some embodiments, the lower melting metalparticles may also serve as a fluxing agent; for example as described inU.S. Pat. No. 6,858,050 (Palmgren).

The loose powder particles may optionally be modified to improve theirflowability and the uniformity of the layer spread. Methods of improvingthe powders include agglomeration, spray drying, gas or wateratomization, flame forming, granulation, milling, and sieving.Additionally, flow agents such as, for example, fumed silica,nanosilica, stearates, and starch may optionally be added.

In order to achieve fine resolution, the loose powder particles arepreferably sized (e.g., by screening) to have a maximum size of lessthan or equal to 400 microns, preferably less than or equal to 250microns, more preferably less than or equal to 200 microns, morepreferably less than or equal to 150 microns, less than or equal to 100microns, or even less than or equal to 80 microns, although larger sizesmay also be used. In certain embodiments, the loose powder particleshave an average particle diameter of less than or equal to one micron(e.g., “submicron”); for example less than or equal to 500 nanometers(nm), or even less than or equal to 150 nm. The various components ofthe loose powder particles may have the same or different maximumparticle sizes, D₉₀, D₅₀, and/or D₁₀ particle size distributionparameters.

Referring to FIG. 1A again, heat 170 is selectively applied viaconduction or irradiation, to heat treat an (e.g., predetermined) area180 of the layer 138. The source 150 of the heat is not particularlylimited, and includes for instance and without limitation, a singlesource or a multipoint source. Suitable single point sources include forinstance, a heated tip 156 and a laser 158. A heated tip typicallyincludes a heated metal tip or a heated ceramic tip, such as a metal tipfound on a common soldering tool. The skilled practitioner can select asuitable low powered laser, for instance, the CUBE 405-100C Diode LaserSystem from Coherent Inc. (Santa Clara, Calif.). Useful multipointsources include a thermal print head, such as commonly used in directthermal printing or thermal transfer printing, and two or more lasers.For instance, one suitable thermal print head is modelKEE-57-24GAG4-STA, available from KYOCERA Corporation (Kyoto, Japan).Hence, referring to FIG. 1B, the third step of the process of FIG. 1A isshown with a thermal print head 152 heat source. A film 154 is disposedon the layer 138 to provide a barrier between the thermal print head 152heat source and the area 180 of the layer 138. Suitable films include,for instance and without limitation, polyethylene terephthalate (PET),polyethylene naphthalate (PEN), polyimide, polytetrafluoroethylene(PTFE), perfluoroalkoxy (PFA), and other films known to be stable athigh temperatures.

Referring to FIG. 1C, the third step of the process of FIG. 1A is shownwith a single tip 156 heat source. A film 154 is disposed on the layer138 to provide a barrier between the single tip 156 heat source and thearea 180 of the layer 138. Referring now to FIG. 1D, the third step ofthe process of FIG. 1A is shown with a laser 158 heat source. FIG. 1Dfurther includes the laser beam 170 being directed at the area 180 ofthe layer 138. No film is provided in this illustrated exemplaryembodiment.

The heat softens and/or melts organic compound particles in the selectedarea 180 of the layer 138, to bond the loose powder particles togetheraccording to a predetermined pattern (and ultimate 3-D shape uponmultiple repetitions). In certain embodiments in which the heat isapplied using a single heated tip, the tip optionally further appliespressure to the (e.g., predetermined) area of the layer of loose powderparticles. An advantage of applying pressure is that the pressure may beeffective to densify the powder particles, especially when the loosepowder particles contain a large amount of organic compound particles.

Referring again to FIG. 1A, the organic compound material bonds togetherthe loose powder particles in at least one predetermined region (orarea) of the loose powder particles to form a layer of bonded powderparticles; for example, by softening and/or melting at least a portionof the organic compound particles.

The above steps are then repeated (step 185) with changes to the regionwhere applying heat is carried out according to a predetermined designresulting through repetition, layer on layer, in a three-dimensional(3-D) abrasive article preform. In each repetition, the loose powderparticles may be independently selected; that is, some or all of theloose powder particles may be the same as, or different from those inadjacent deposited layers.

The abrasive article preform comprises the bonded powder particles andremaining loose powder particles. Once sufficient repetitions have beencarried out to form the abrasive article preform, it is preferablyseparated from substantially all (e.g., at least 85 percent, at least 90percent, preferably at least 95 percent, and more preferably at least 99percent) of the remaining loose powder particles, although this is not arequirement. In certain embodiments, at least a portion of the organiccompound material is burned off (e.g., volatilizing and/or decomposing)following the separation of the bonded powder particles and prior to orconcurrently with infusing with a metal.

If desired, multiple particle reservoirs each containing a differentpowder may be used. Likewise, multiple different organic compoundparticles may be used. This results in different powders/bindersdistributed in different and discrete regions of the abrasive article.For example, relatively inexpensive, but lower performing abrasiveparticles and/or vitreous bond precursor particles may be relegated toregions of a vitrified bond abrasive article where it is notparticularly important to have high performance properties (e.g., in theinterior away from the abrading surface). The same approach can apply tometal bond abrasive articles.

In another aspect, the present disclosure provides a vitreous bondabrasive article precursor. The vitreous bond abrasive article precursorcomprises abrasive particles bonded together by a vitreous bondprecursor material and an organic compound, wherein the vitreous bondabrasive article precursor further comprises at least one of: at leastone tortuous cooling channel extending at least partially through thevitreous bond abrasive article precursor; or at least one arcuatecooling channel extending at least partially through the vitreous bondabrasive article precursor. The abrasive particles often include atleast one of silicon carbide, boron carbide, silicon nitride, or metaloxide ceramic particles.

Generally, vitreous bond abrasive articles made in ways according to thepresent disclosure have considerable porosity throughout their volumes.Accordingly, the abrasive article preform may then be infused with asolution or dispersion of additional vitreous bond precursor material,or grain growth modifiers.

In embodiments in which the loose powder particles include highermelting metal particles and lower melting metal particles, the abrasivearticle preform may be heated sufficiently to cause the lower meltingmetal particles to soften/melt and bond to at least a portion of theloose powder particles, and then cooled to provide the metal bondabrasive article. In embodiments in which the loose powder particlesinclude higher melting metal particles and no lower melting metalparticles, the abrasive article preform may be heated sufficiently tocause the higher melting metal particles to at least sinter and bond toat least a portion of the loose powder particles, and then cooled toprovide the metal bond abrasive article. Cooling may be accomplished byany means known to the art; for example cold quenching or air cooling toroom temperature.

Metal bond abrasive articles and/or abrasive article preforms madeaccording to the present disclosure may comprise a porousmetal-containing matrix (e.g., which may comprise metal particles andabrasive particles, and which may be sintered) with considerableporosity throughout its volume, although this is not a requirement. Forexample, the porous metal-containing matrix may have a void fraction of1 to 60 volume percent, preferably 5 to 50 volume percent, and morepreferably 15 to 50 volume percent, more preferably 40 to 50 volumepercent, although this is not a requirement. Accordingly, the abrasivearticle preform may then be infused with a molten metal that has atemperature below the melting point(s) of any other metallic components,then cooled. Examples of suitable metals that can be made molten andinfused into the abrasive article preform include aluminum, indium,brass, bronze, silver, copper, gold, lead, cobalt, magnesium, nickel,zinc, tin, iron, chromium, silicon alloys, alloys of the foregoing, andcombinations thereof.

Further details concerning sintering and then infusing with molten metalcan be found in, for example, U.S. Pat. No. 2,367,404 (Kott) and U.S.Pat. Appln. Publ. No. 2002/095875 (D'Evelyn et al.).

Advantageously, methods according to the present disclosure are suitablefor manufacturing various metal bond abrasive articles that cannot bereadily or easily fabricated by other methods. For example, inclusion ofinternal voids is possible as long as an opening to the exterior of theabrasive preform exists for removal of unbonded loose powder.Accordingly, cooling channels having tortuous and or arcuate paths canbe readily manufactured using methods of the present disclosure. Coolingchannels are open to the exterior of the metal bond abrasive article. Insome embodiments, they have a single opening, but more typically theyhave two or more openings. A cooling medium (e.g., air, water, emulsion,or oil) circulates through the cooling channel(s) to remove heatgenerated during the abrading process.

Accordingly, in another aspect, the present disclosure provides a metalbond abrasive article precursor comprising metallic particles andabrasive particles bonded together by an organic compound material,wherein the metal bond abrasive article precursor further comprises atleast one of: at least one tortuous cooling channel extending at leastpartially through the metal bond abrasive article precursor; at leastone arcuate cooling channel extending at least partially through themetal bond abrasive article precursor.

The abrasive article preform 190 is then heated (step 195 in FIG. 1A) toremove any organic compound material that may be present, and sinter theabrasive particles with the metal or vitreous bond precursor particles(e.g., by burning off the organic compound material), thereby providingthe metal bond or vitreous bond abrasive article, respectively.

In certain embodiments, the vitreous bond or metal bond abrasive articleis selected from the group consisting of a unitary structured abrasivedisc, an abrasive grinding bit, abrasive segments, abrasive rims, shapedabrasive particles (e.g., triangular abrasive particles), and anabrasive wheel, as well as many hitherto unknown vitreous bond or metalbond abrasive articles. In some preferred embodiments, a metal bondabrasive article comprises at least a portion of a rotary dental tool(e.g., a dental drill bit, a dental bur, or a dental polishing tool).

Referring now to FIG. 2 , an exemplary vitreous bond or metal bondabrasive wheel 200 has arcuate and tortuous cooling channels 220,respectively.

FIG. 3 shows another exemplary vitreous bond or metal bond abrasivewheel 300 that has tortuous cooling channels 320.

FIG. 4 shows an exemplary vitreous bond or metal bond abrasive segment400. In typical use, multiple vitreous bond or metal bond abrasivesegments 400 are mounted evenly spaced along the circumference of ametal disc to form an abrasive wheel.

FIG. 5 shows a vitreous bond or metal bond abrasive disc 500 has tworegions 510, 520. Each region has abrasive particles 530, 540 retainedin a vitreous bond or metal bond matrix material 550, 560, respectively.

FIGS. 6A-6B and 7A-7B, respectively show various unitary structuredabrasive discs with precisely-shaped ceramic abrasive elements 610, 710formed integrally with ceramic planar bases 620, 720.

FIG. 8 shows a rotary abrasive tool 800 (a bit for a handheld motordriven shaft such as, for example, a Dremel tool).

An exemplary dental bur 900 is shown in FIG. 9 . Referring now to FIG. 9, dental bur 900 includes head 930 secured to shank 920. Dental bur 900comprises abrasive particles 905 secured in porous metal bond orvitreous bond 910.

The foregoing abrasive wheels shown in FIGS. 2 and 3 can be prepared byfiring corresponding green bodies (i.e., having the same general shapefeatures, but comprising a vitreous bond or metal bond precursorparticles held together by a temporary binder).

In some embodiments, a (e.g., non-transitory) machine-readable medium isemployed in additive manufacturing of vitreous bond abrasive articlesand/or metal bond abrasive articles according to at least certainaspects of the present disclosure. Data is typically stored on themachine-readable medium. The data represents a three-dimensional modelof a vitreous bond abrasive article or a metal bond abrasive article,which can be accessed by at least one computer processor interfacingwith additive manufacturing equipment (e.g., a 3D printer, amanufacturing device, etc.). The data is used to cause the additivemanufacturing equipment to create at least a vitreous bond abrasivearticle precursor or preform or a metal bond abrasive article precursoror preform.

Data representing a vitreous bond abrasive article or a metal bondabrasive article may be generated using computer modeling such ascomputer aided design (CAD) data. Image data representing the vitreousbond abrasive article and/or metal bond abrasive article design can beexported in STL format, or in any other suitable computer processableformat, to the additive manufacturing equipment. Scanning methods toscan a three-dimensional object may also be employed to create the datarepresenting the vitreous bond abrasive article or metal bond abrasivearticle. One exemplary technique for acquiring the data is digitalscanning. Any other suitable scanning technique may be used for scanningan article, including X-ray radiography, laser scanning, computedtomography (CT), magnetic resonance imaging (MRI), and ultrasoundimaging. Other possible scanning methods are described, e.g., in U.S.Patent Application Publication No. 2007/0031791 (Cinader, Jr., et al.).The initial digital data set, which may include both raw data fromscanning operations and data representing articles derived from the rawdata, can be processed to segment an abrasive article design from anysurrounding structures (e.g., a support for the abrasive article).

Often, machine-readable media are provided as part of a computingdevice. The computing device may have one or more processors, volatilememory (RAM), a device for reading machine-readable media, andinput/output devices, such as a display, a keyboard, and a pointingdevice. Further, a computing device may also include other software,firmware, or combinations thereof, such as an operating system and otherapplication software. A computing device may be, for example, aworkstation, a laptop, a personal digital assistant (PDA), a server, amainframe or any other general-purpose or application-specific computingdevice. A computing device may read executable software instructionsfrom a computer-readable medium (such as a hard drive, a CD-ROM, or acomputer memory), or may receive instructions from another sourcelogically connected to computer, such as another networked computer.Referring to FIG. 10 , a computing device 1000 often includes aninternal processor 1080, a display 1100 (e.g., a monitor), and one ormore input devices such as a keyboard 1140 and a mouse 1120. In FIG. 10, a rotary abrasive tool 1130 is shown on the display 1100.

Referring to FIG. 11 , in certain embodiments, the present disclosureprovides a system 1150. The system 1150 comprises a display 1160 thatdisplays a 3D model 1155 of a metal bond abrasive article (e.g., arotary abrasive tool 1130 as shown on the display 1100 of FIG. 10 ); andone or more processors 1165 that, in response to the 3D model 1155selected by a user, cause a 3D printer/additive manufacturing device1175 to create a physical object of a metal bond abrasive articleprecursor 1180 of the metal bond abrasive article. The metal bondabrasive article precursor 1180 comprises metallic particles andabrasive particles bonded together by an organic compound material. Themetal bond abrasive article precursor 1180 further comprises at leastone of at least one tortuous cooling channel extending at leastpartially through the metal bond abrasive article precursor; and atleast one arcuate cooling channel extending at least partially throughthe metal bond abrasive article precursor. Similarly, in certainembodiments a system 1150 comprises a display 1160 that displays a 3Dmodel 1155 of a vitreous bond abrasive article; and one or moreprocessors 1165 that, in response to the 3D model 1155 selected by auser, cause a 3D printer/additive manufacturing device 1175 to create aphysical object of a vitreous bond abrasive article precursor 1180 ofthe vitreous bond abrasive article. The vitreous bond abrasive articleprecursor 1180 comprises abrasive particles bonded together by avitreous bond precursor material and an organic compound. The vitreousbond abrasive article precursor 1180 further comprises at least one ofat least one tortuous cooling channel extending at least partiallythrough the vitreous bond abrasive article precursor; or at least onearcuate cooling channel extending at least partially through thevitreous bond abrasive article precursor.

Referring to FIG. 12 , a processor 1220 (or more than one processor) isin communication with each of a machine-readable medium 1210 (e.g., anon-transitory medium), a 3D printer/additive manufacturing device 1240,and optionally a display 1230 for viewing by a user. The 3Dprinter/additive manufacturing device 1240 is configured to make one ormore articles 1250 based on instructions from the processor 1220providing data representing a 3D model of the article 1250 from themachine-readable medium 1210.

Referring to FIG. 13 , for example and without limitation, an additivemanufacturing method comprises retrieving 1310, from a (e.g.,non-transitory) machine-readable medium, data representing a 3D model ofa vitreous bond abrasive article or a metal bond abrasive articleaccording to at least one embodiment of the present disclosure. Themethod further includes executing 1320, by one or more processors, anadditive manufacturing application interfacing with a manufacturingdevice using the data; and generating 1330, by the manufacturing device,a physical object of the vitreous bond abrasive article or metal bondabrasive article. The additive manufacturing equipment can selectivelybond the metallic particles or vitreous bond precursor particles withthe abrasive particles and organic compound material according to a setof computerized design instructions to create a desired metal bondabrasive article precursor or preform or vitreous bond abrasive articleprecursor or preform, respectively. One or more various optionalpost-processing steps 1340 may be undertaken. For instance, optionally,the metal bond abrasive article precursor or preform or vitreous bondabrasive article precursor or preform is heated to form the metal bondabrasive article or the vitreous bond abrasive article, respectively.Additionally, referring to FIG. 14 , methods of forming a metal bondabrasive article precursor or preform or a vitreous bond abrasivearticle precursor or preform comprise receiving 1410, by a manufacturingdevice having one or more processors, a digital object comprising dataspecifying a plurality of layers of a metal bond abrasive article or avitreous bond abrasive article; and generating 1420, with themanufacturing device by an additive manufacturing process, the metalbond abrasive article precursor or preform or vitreous bond abrasivearticle precursor or preform, respectively, based on the digital object.Again, the article may undergo one or more steps of post-processing1430.

Select Embodiments of the Present Disclosure

Embodiment 1 is a method of making a vitreous bond abrasive article, themethod comprising sequential steps:

a) a subprocess comprising sequentially:

-   -   i) depositing a layer of loose powder particles in a confined        region, wherein the loose powder particles comprise vitreous        bond precursor particles, abrasive particles, and organic        compound particles, and wherein the layer of loose powder        particles has substantially uniform thickness; and    -   ii) selectively applying heat via conduction or irradiation, to        heat treat an area of the layer of loose powder particles;

b) independently carrying out step a) a plurality of times to generatean abrasive article preform comprising the bonded powder particles andremaining loose powder particles, wherein in each step a), the loosepowder particles are independently selected;

c) separating substantially all of the remaining loose powder particlesfrom the abrasive article preform; and

d) heating the abrasive article preform to provide the vitreous bondabrasive article comprising the abrasive particles retained in avitreous bond material.

Embodiment 2 is the method of embodiment 1, wherein the abrasiveparticles include at least one of diamond particles or cubic boronnitride particles.

Embodiment 3 is the method of embodiment 1, wherein the abrasiveparticles include metal oxide ceramic particles.

Embodiment 4 is the method of any of embodiments 1 to 3, wherein theabrasive particles and the vitreous bond material have the same chemicalcomposition.

Embodiment 5 is the method of any of embodiments 1 to 4, wherein thevitreous bond abrasive article includes at least one cooling channel.

Embodiment 6 is the method of any of embodiments 1 to 5, wherein thevitreous bond abrasive article is selected from the group consisting ofa unitary structured abrasive disc, an abrasive grinding bit, abrasivesegments, abrasive rims, and an abrasive wheel.

Embodiment 7 is the method of any of embodiments 1 to 6, wherein theorganic compound particles have a melting point between 50 degreesCelsius and 250 degrees Celsius, inclusive.

Embodiment 8 is the method of any of embodiments 1 to 7, wherein theorganic compound particles have a melting point between 100 degreesCelsius to 180 degrees Celsius, inclusive.

Embodiment 9 is the method of any of embodiments 1 to 8, wherein theorganic compound particles are selected from waxes, sugars, dextrins,thermoplastics having a melting point of no greater than 250 degreesCelsius, acrylates, methacrylates, and combinations thereof.

Embodiment 10 is the method of any of embodiments 7 to 9, wherein theorganic compound particles are selected from waxes, acrylates,methacrylates, polyethyleneterephthalate (PET), polylactic acid (PLA),and combinations thereof.

Embodiment 11 is the method of any of embodiments 1 to 10, wherein theorganic compound particles are present in an amount of 2.5 weightpercent to 30 weight percent of the loose powder particles.

Embodiment 12 is the method of any of embodiments 1 to 11, wherein theorganic compound particles are present in an amount of 5 weight percentto 20 weight percent of the loose powder particles.

Embodiment 13 is the method of embodiment 11 or embodiment 12, whereinthe inorganic vitreous bond precursor includes a precursor of alphaalumina.

Embodiment 14 is the method of any of embodiments 8 to 13, wherein theloose powder particles include submicron ceramic particles.

Embodiment 15 is the method of any of embodiments 1 to 14, wherein theloose powder particles further include flow agent particles.

Embodiment 16 is the method of any of embodiments 1 to 15, wherein stepd) further includes burning out the organic compound material.

Embodiment 17 is the method of any of embodiments 1 to 16, wherein instep ii) the heat is applied using a single heated tip or a thermalprint head.

Embodiment 18 is the method of claim 17, wherein in step ii) the singleheated tip further applies pressure to the area of the layer of loosepowder particles.

Embodiment 19 is the method of any of embodiments 1 to 16, wherein instep ii) the heat is applied using at least one laser.

Embodiment 20 is a vitreous bond abrasive article precursor includingabrasive particles bonded together by a vitreous bond precursor materialand an organic compound, wherein the vitreous bond abrasive articleprecursor further includes at least one of at least one tortuous coolingchannel extending at least partially through the vitreous bond abrasivearticle precursor; or at least one arcuate cooling channel extending atleast partially through the vitreous bond abrasive article precursor.

Embodiment 21 is the vitreous bond abrasive precursor of embodiment 20,wherein the abrasive particles include at least one of silicon carbide,boron carbide, silicon nitride, or metal oxide ceramic particles.

Embodiment 22 is a method of making a metal bond abrasive article, themethod comprising sequential steps:

a) a subprocess comprising sequentially:

-   -   i) depositing a layer of loose powder particles in a confined        region, wherein the loose powder particles comprise higher        melting metal particles, abrasive particles, and organic        compound particles, and wherein the layer of loose powder        particles has substantially uniform thickness; and    -   ii) selectively applying heat via conduction or irradiation, to        heat treat an area of the layer of loose powder particles;

b) independently carrying out step a) a plurality of times to generatean abrasive article preform comprising the bonded powder particles andremaining loose powder particles, wherein in each step a), the loosepowder particles are independently selected;

c) separating substantially all of the remaining loose powder particlesfrom the abrasive article preform;

d) infusing the abrasive article preform with a molten lower meltingmetal, wherein at least some of the higher melting metal particles donot completely melt when contacted by the molten lower melting metal;and

e) solidifying the molten lower melting metal to provide the metal bondabrasive article.

Embodiment 23 is the method of embodiment 22, wherein the loose powderparticles further include fluxing agent particles.

Embodiment 24 is the method of embodiment 22 or embodiment 23, whereinthe abrasive particles include at least one of diamond particles orcubic boron nitride particles.

Embodiment 25 is the method of embodiment 22 or embodiment 23, whereinthe abrasive particles include metal oxide ceramic particles.

Embodiment 26 is the method of any of embodiments 22 to 25, wherein themetal bond abrasive article includes at least one cooling channel.

Embodiment 27 is the method of any of embodiments 22 to 26, wherein themetal bond abrasive article is selected from the group consisting of anabrasive pad, an abrasive grinding bit, abrasive segments, and anabrasive wheel.

Embodiment 28 is the method of any of embodiments 22 to 26, wherein themetal bond abrasive article comprises at least a portion of a rotarydental tool.

Embodiment 29 is the method of any of embodiments 22 to 28, wherein theorganic compound particles have a melting point between 50 degreesCelsius and 250 degrees Celsius, inclusive.

Embodiment 30 is the method of any of embodiments 22 to 29, wherein theorganic compound particles have a melting point between 100 degreesCelsius to 180 degrees Celsius, inclusive.

Embodiment 31 is the method of any of embodiments 22 to 30, wherein theorganic compound particles are selected from waxes, sugars, dextrins,thermoplastics having a melting point of no greater than 250 degreesCelsius, acrylates, methacrylates, and combinations thereof.

Embodiment 32 is the method of any of embodiments 29 to 31, wherein theorganic compound particles are selected from waxes, acrylates,methacrylates, polyethyleneterephthalate (PET), polylactic acid (PLA),and combinations thereof.

Embodiment 33 is the method of any of embodiments 22 to 32, wherein theorganic compound particles are present in an amount of 1.5 weightpercent to 25 weight percent of the loose powder particles.

Embodiment 34 is the method of any of embodiments 22 to 33, wherein theorganic compound particles are present in an amount of 3 weight percentto 20 weight percent of the loose powder particles.

Embodiment 35 is the method of any of embodiments 22 to 34, wherein thehigher melting metal particles have a melting point that is at least 50degrees Celsius higher than the temperature of the molten lower meltingmetal.

Embodiment 36 is the method of any of embodiments 22 to 35, furthercomprising, between steps c) and d), burning off at least a portion ofthe organic compound material.

Embodiment 37 is the method of any of embodiments 22 to 36, wherein instep ii) the heat is applied using a single heated tip or a thermalprint head.

Embodiment 38 is the method of embodiment 37, wherein in step ii) thesingle heated tip further applies pressure to the area of the layer ofloose powder particles.

Embodiment 39 is the method of any of embodiments 22 to 36, wherein instep ii) the heat is applied using at least one laser.

Embodiment 40 is a method of making a metal bond abrasive article, themethod comprising sequential steps:

a) a subprocess comprising sequentially:

-   -   i) depositing a layer of loose powder particles in a confined        region, wherein the loose powder particles comprise metal        particles, abrasive particles, and organic compound particles,        and wherein the layer of loose powder particles has        substantially uniform thickness;    -   ii) selectively applying heat via conduction or irradiation, to        heat treat an area of the layer of loose powder particles;

b) independently carrying out step a) a plurality of times to generatean abrasive article preform comprising the bonded powder particles andremaining loose powder particles, wherein the abrasive article preformhas a predetermined shape, and wherein in each step a), the loose powderparticles are independently selected;

c) separating substantially all of the remaining loose powder particlesfrom the abrasive article preform; and

d) heating the abrasive article preform to provide the metal bondabrasive article.

Embodiment 41 is the method of embodiment 40, wherein the loose powderparticles further include fluxing agent particles.

Embodiment 42 is the method of embodiment 40 or embodiment 41, whereinthe abrasive particles include at least one of diamond particles orcubic boron nitride particles.

Embodiment 43 is the method of embodiment 40 or embodiment 41, whereinthe abrasive particles include metal oxide ceramic particles.

Embodiment 44 is the method of any of embodiments 40 to 43, wherein themetal particles include a combination of higher melting metal particlesand lower melting metal particles, wherein the higher melting metalparticles have a melting point that is at least 50 degrees Celsiushigher than the temperature of the molten lower temperature metal.

Embodiment 45 is the method of any of embodiments 40 to 44, wherein themetal bond abrasive article includes at least one cooling channel.

Embodiment 46 is the method of any of embodiments 40 to 45, wherein themetal bond abrasive article is selected from the group consisting of anabrasive pad, an abrasive grinding bit, abrasive segments, and anabrasive wheel.

Embodiment 47 is the method of any of embodiments 40 to 45, wherein themetal bond abrasive article includes at least a portion of a rotarydental tool.

Embodiment 48 is the method of any of embodiments 40 to 47, wherein theorganic compound particles have a melting point between 50 degreesCelsius and 250 degrees Celsius, inclusive.

Embodiment 49 is the method of any of embodiments 40 to 48, wherein theorganic compound particles have a melting point between 100 degreesCelsius to 180 degrees Celsius, inclusive.

Embodiment 50 is the method of any of embodiments 40 to 49, wherein theorganic compound particles are selected from waxes, sugars, dextrins,thermoplastics having a melting point of no greater than 250 degreesCelsius, acrylates, methacrylates, and combinations thereof.

Embodiment 51 is the method of any of embodiments 48 to 50, wherein theorganic compound particles are selected from waxes, acrylates,methacrylates, polyethyleneterephthalate (PET), polylactic acid (PLA),and combinations thereof.

Embodiment 52 is the method of any of embodiments 40 to 51, wherein theorganic compound particles are present in an amount of 1.5 weightpercent to 25 weight percent of the loose powder particles.

Embodiment 53 is the method of any of embodiments 40 to 52, wherein theorganic compound particles are present in an amount of 3 weight percentto 20 weight percent of the loose powder particles.

Embodiment 54 is the method of any of embodiments 40 to 53, wherein instep ii) the heat is applied using a single heated tip or a thermalprint head.

Embodiment 55 is the method of embodiment 54, wherein in step ii) thesingle heated tip further applies pressure to the area of the layer ofloose powder particles.

Embodiment 56 is the method of any of embodiments 40 to 53, wherein instep ii) the heat is applied using at least one laser.

Embodiment 57 is a metal bond abrasive article precursor includingmetallic particles and abrasive particles bonded together by an organiccompound material, wherein the metal bond abrasive article precursorfurther includes at least one of: at least one tortuous cooling channelextending at least partially through the metal bond abrasive articleprecursor; and at least one arcuate cooling channel extending at leastpartially through the metal bond abrasive article precursor.

Embodiment 58 is a non-transitory machine readable medium having datarepresenting a three-dimensional model of a vitreous bond abrasivearticle, when accessed by one or more processors interfacing with a 3Dprinter, causes the 3D printer to create a vitreous bond abrasivearticle precursor of the vitreous bond abrasive article. The vitreousbond abrasive article precursor includes abrasive particles bondedtogether by a vitreous bond precursor material and an organic compound.The vitreous bond abrasive article precursor further includes at leastone of at least one tortuous cooling channel extending at leastpartially through the vitreous bond abrasive article precursor; or atleast one arcuate cooling channel extending at least partially throughthe vitreous bond abrasive article precursor.

Embodiment 59 is a method including retrieving, from a (e.g.,non-transitory) machine readable medium, data representing a 3D model ofa vitreous bond abrasive article. A vitreous bond abrasive articleprecursor of the vitreous bond abrasive article preform includesabrasive particles bonded together by a vitreous bond precursor materialand an organic compound. The vitreous bond abrasive article precursorfurther includes at least one of at least one tortuous cooling channelextending at least partially through the vitreous bond abrasive articleprecursor; or at least one arcuate cooling channel extending at leastpartially through the vitreous bond abrasive article precursor. Themethod further includes executing, by one or more processors, a 3Dprinting application interfacing with a manufacturing device using thedata; and generating, by the manufacturing device, a physical object ofthe vitreous bond abrasive article precursor.

Embodiment 60 is a vitreous bond abrasive article precursor generatedusing the method of embodiment 59.

Embodiment 61 is a method including receiving, by a manufacturing devicehaving one or more processors, a digital object comprising dataspecifying a plurality of layers of a vitreous bond abrasive articleprecursor. The vitreous bond abrasive article precursor includesabrasive particles bonded together by a vitreous bond precursor materialand an organic compound. The vitreous bond abrasive article precursorfurther includes at least one of at least one tortuous cooling channelextending at least partially through the vitreous bond abrasive articleprecursor; or at least one arcuate cooling channel extending at leastpartially through the vitreous bond abrasive article precursor. Themethod further includes generating, with the manufacturing device by anadditive manufacturing process, the vitreous bond abrasive articleprecursor based on the digital object.

Embodiment 62 is the method of embodiment 61, further includingseparating loose powder particles from the vitreous bond abrasivearticle precursor; and heating the abrasive article precursor to providethe vitreous bond abrasive article including the abrasive particlesretained in a vitreous bond material.

Embodiment 63 is the method of embodiment 62, further including burningout the organic compound material.

Embodiment 64 is a system including a display that displays a 3D modelof a vitreous bond abrasive article; and one or more processors that, inresponse to the 3D model selected by a user, cause a 3D printer tocreate a physical object of a vitreous bond abrasive article precursorof the vitreous bond abrasive article. The vitreous bond abrasivearticle precursor includes abrasive particles bonded together by avitreous bond precursor material and an organic compound. The vitreousbond abrasive article precursor further includes at least one of atleast one tortuous cooling channel extending at least partially throughthe vitreous bond abrasive article precursor; or at least one arcuatecooling channel extending at least partially through the vitreous bondabrasive article precursor.

Embodiment 65 is a non-transitory machine readable medium having datarepresenting a three-dimensional model of a metal bond abrasive article,when accessed by one or more processors interfacing with a 3D printer,causes the 3D printer to create the metal bond abrasive articleprecursor of the metal bond abrasive article. The metal bond abrasivearticle precursor includes metallic particles and abrasive particlesbonded together by an organic compound material. The metal bond abrasivearticle precursor further includes at least one of at least one tortuouscooling channel extending at least partially through the metal bondabrasive article precursor; and at least one arcuate cooling channelextending at least partially through the metal bond abrasive articleprecursor.

Embodiment 66 is a method including retrieving, from a non-transitorymachine readable medium, data representing a 3D model of a metal bondabrasive article precursor. The metal bond abrasive article precursorincludes metallic particles and abrasive particles bonded together by anorganic compound material. The metal bond abrasive article precursorfurther includes at least one of at least one tortuous cooling channelextending at least partially through the metal bond abrasive articleprecursor; and at least one arcuate cooling channel extending at leastpartially through the metal bond abrasive article precursor. The methodfurther includes executing, by one or more processors, a 3D printingapplication interfacing with a manufacturing device using the data; andgenerating, by the manufacturing device, a physical object of the metalbond abrasive article precursor.

Embodiment 67 is a metal bond abrasive article precursor generated usingthe method of embodiment 66.

Embodiment 68 is a method including receiving, by a manufacturing devicehaving one or more processors, a digital object comprising dataspecifying a plurality of layers of a metal bond abrasive articleprecursor. The metal bond abrasive article precursor includes metallicparticles and abrasive particles bonded together by an organic compoundmaterial. The metal bond abrasive article precursor further includes atleast one of at least one tortuous cooling channel extending at leastpartially through the metal bond abrasive article precursor; and atleast one arcuate cooling channel extending at least partially throughthe metal bond abrasive article precursor. The method further includesgenerating, with the manufacturing device by an additive manufacturingprocess, the metal bond abrasive article precursor based on the digitalobject.

Embodiment 69 is the method of embodiment 68, further includingseparating loose powder particles from the metal bond abrasive articlepreform; infusing the abrasive article preform with a molten lowermelting metal, wherein at least some of the metallic particles do notcompletely melt when contacted by the molten lower melting metal; andsolidifying the molten lower melting metal to provide the metal bondabrasive article.

Embodiment 70 is a system including a display that displays a 3D modelof a metal bond abrasive article; and one or more processors that, inresponse to the 3D model selected by a user, cause a 3D printer tocreate a physical object of a metal bond abrasive article precursor ofthe metal bond abrasive article. The metal bond abrasive articleprecursor includes metallic particles and abrasive particles bondedtogether by an organic compound material. The metal bond abrasivearticle precursor further includes at least one of at least one tortuouscooling channel extending at least partially through the metal bondabrasive article precursor; and at least one arcuate cooling channelextending at least partially through the metal bond abrasive articleprecursor.

EXAMPLES

Unless otherwise noted, all parts, percentages, ratios, etc. in theExamples and the rest of the specification are by weight.

TABLE 1 ABBREVIATION DESCRIPTION PDR1 ALODUR BFRPL aluminium oxideparticles, grade P320, from Treibacher Schleifmittel AG (Villach,Austria) PDR2 A mix of 98.5% vitrified bond VO82069 from Reimbold &Strick, Cologne, Germany and 1.5% color stain for glazes K90084 fromReimbold & Strick (Cologne, Germany) PDR3 MicroKlear 116, a micronizedblend of polyethylene and carnauba wax, particle size of 4.5 to 5.5micron, maximum particle size 15.6 micron, melting point 248-257 degreeF., from Micro Powders, Inc. (Tarrytown, New York) PDR4 MicroPro 400, amicronized polypropylene wax, particle size of 5.0 to 7.0 micron,maximum particle size 22 micron, melting point 284-289 degreesFahrenheit (140-143 degrees Celsius), from Micro Powders, Inc.(Tarrytown, New York)

Example 1

A print material P1 was prepared by mixing, based on the mixture weight,77.3 wt. % of PDR1, 13.6 wt. % of PDR2, and 9.1 wt. % of PDR3. Thepowder mixture was put in glass jar and rotated on a rolling bank mixerat about 50 rpm for 15 minutes. The print material was spread on a pieceof paper using a straight metal blade, and one sheet of paper was usedas a shim and the thickness of the resulting first powder layer wasapproximately 100 microns. It was covered with a 2 mil (50.8micrometers) thick PET film. A soldering iron was heated toapproximately 425° F. (˜218° C.), and the hot tip was slowly moved overa predetermined approximately 1 centimeter (cm)×1 cm area. Only slightpressure was applied and the PET film was barely deformed. Then the PETfilm was removed, and it was observed that the print material P1 hadturned from slightly grey to dark grey in the area where the heated tiphad touched the PET film. Using a second layer of paper as a shim, asecond 0.1 millimeter (mm) thick layer of print material was spread ontop of the first layer of print material. It was again covered with thePET film, and the same 1 cm×1 cm area was heated with the tip of thesoldering iron again. The procedure then was repeated for a third layer.After the PET film was removed, a solid object was extracted from theloose powder. It was observed that the three layers had melted togetherto form a green body. The green body then was placed into a furnace andburned out at 400° C. for 2 hours, followed by sintering at 700° C. for4 hours, resulting in an abrasive square that measured approximately 1cm×1 cm and 0.3 mm in thickness.

Example 2

Experimental Apparatus and Preparations

A laser marking device was assembled, consisting of a CO2 laser, ModelE-400, available from Coherent, Santa Clara, Calif., and a 3-AxisModular Scanner, Model HPLK 1330-17, CO2 30 MM, available from GSIGroup, Inc, Billerica, Mass. The device was controlled by a computerrunning the WaveRunner Advanced Laser Scanning Software, Version 3.3.5build-0200, by Nutfield Technology, Hudson, N.H.

In the WaveRunner scanning software program, a 1.5 cm square shape wasdrawn in the approximate center of the scanning field. The “Hatch”function was enabled within the program and used to cross-hatch thesquare. The first hatch pattern was at an angle of 0 degrees, and thesecond hatch pattern was at an angle of 90 degrees. In both hatchpatterns, the lines were set at a distance of 0.5 mm apart. Only thehatch patterns were marked; the contour of the shape was not.

The laser scanning conditions were set in WaveRunner as follows: Speed2000 mm/second, Power: 8%, Frequency 20 kHz. A power setting of 8%equals a laser beam power of 27.8 Watts.

Experimental Procedure

Two sheets of paper were put down in the laser scanning area of thelaser marking device. On top of the paper, the print material P1 wasspread using a straight metal blade, and two sheets of paper, layered ontop of each other, were used as a shim and the thickness of theresulting first powder layer was approximately 200 microns. This firstpowder layer then was marked with the laser scanner, using theconditions described above. It was observed that the print material P1had turned from slightly grey to dark grey in the area where the laserhad marked the layer. A second and a third layer of print material P1,each 200 micron in thickness, were subsequently put down and marked thesame way. Finally, a fourth layer was put down on the previous threelayers, and this final layer was marked with two passes of the laser.

A solid object was extracted from the loose powder. It was observed thatthe four layers had melted together and formed a green body that couldbe safely handled without breaking apart.

The green body then was placed into a furnace and burned out at 400° C.for 2 hours, followed by sintering at 700° C. for 4 hours, resulting inan abrasive square that measured approximately 1.5 cm×1.5 cm and 0.8 mmin thickness.

Example 3

Experimental Apparatus and Preparations

An apparatus for 3D printing with powders was constructed as generallydepicted in FIG. 1 . Two adjacent chambers, each measuring about 3inches×2 inches (7.62 cm×5.08 cm) in the xy plane and 2 inches (5.08 cm)in the z-direction, were milled into a 2 inch (5.08 cm) thick aluminumblock. Two tightly fitting square pistons made from aluminum wereinserted into the chambers and connected to stepper motor linearactuators, VersaDrive 17, Model USV17-110-AB-0506, with a 6 inch (15.24)long lead screw, available from USAutomation, Mission Viejo, Calif. Onechamber and piston was designated the powder supply, the other wasdesignated the build chamber. The linear actuators allow the pistons tobe moved up and down in z-direction. A rotating aluminum roller, drivenby a motor, was mounted in the plane about 1 mm above the chambers. Thisroller was actuated in x-direction using a stepper motor linearactuator, VersaDrive 17, Model USV17-110-AB-2512, with a 12 inch (30.48cm) long lead screw, available from USAutomation, Mission Viejo, Calif.This actuated roller allows movement of powder from the powder supplychamber to the build chamber.

The motors were connected to a motion controller board, model EZ4AXIS,available from AllMotion, Union City, Calif. The motion controller wasprogrammed to run the following sequence: First, lower the build pistonby 0.10 mm, then raise the powder supply piston by 0.16 mm, then switchon the roller motor, actuate the roller to move powder from the powdersupply chamber to the build chamber, stop the roller motor, and returnthe roller to the origin. This procedure produces a uniform, 0.1 mmthick layer of powder in the build area. Above the two chamber assembly,a motorized xy positioning stage was mounted, and a 500 mW, 405 nm diodelaser, model M-33A405-500-G, available from TEM-Laser, Wuhan, Hubei,China, was attached. The xy table contained a Grbl controller board forlaser engravers and was able to be controlled by Grbl 0.9, an opensource software for controlling the motion of machines. The graphicswere loaded into Inkscape 0.48 with a laser engraver plug-in, an opensource graphics software. This software generated the xy motion controland the laser power code from a drawing, and transferred it to the Grbl0.9 software.

A print material P2 was prepared by mixing, based on the mixture weight,77.3 wt. % of PDR1, 13.6 wt. % of PDR2 and 9.1 wt. % of PDR4. The powdermixture was put in a glass jar and rotated on a rolling bank mixer atabout 50 rpm for 15 minutes. The powder supply piston was lowered to thebottom, and the chamber was filled with the print material P2. The buildpiston was raised to the top. Then the powder spreading procedure wasexecuted 10 times to form a uniform powder base in the build area.

In the Inkscape software, the font Arial, font size 14 pt, was selected,and the word “Test” was written. Then the laser engraver plug-in wasselected. The laser was set to 100% output, and a motion speed of 10mm/second was selected, and the Grbl code was generated and transferredto the Grbl 0.9 software. Then a first 0.1 mm thick layer of printmaterial P2 was spread. Next, the Grbl code was executed. It wasobserved that the laser turned on and moved in the shape of the word“Test”, and the powder turned from a light grey to a dark grey in theshape of the word “Test”.

A second layer, also 0.1 mm thick, of print material P2 was spread, andthe Grbl code was executed a second time. This sequence was repeateduntil a total of 20 layers had been spread and exposed to the laser.

Then a spatula was used to remove the object from the surroundingpowder. Loose powder was removed and an object in the shape of the word“Test”, 2.05 mm in thickness, was recovered.

It was observed that the 20 layers had melted together and formed agreen body that could be safely handled without breaking apart. Thegreen body was placed into a furnace and burned out at 400° C. for 2hours, followed by sintering at 700° C. for 4 hours, resulting in anabrasive article in the shape of the word “Test”. The article was rubbedagainst a block of aluminum, and an abrasion pattern was observed.

What is claimed is:
 1. A method of forming a vitreous bond abrasivearticle, the method comprising: receiving, by a manufacturing devicehaving one or more processors, a digital object comprising dataspecifying a plurality of layers of a vitreous bond abrasive articleprecursor, the vitreous bond abrasive article precursor comprising:abrasive particles bonded together by a vitreous bond precursor materialand an organic compound, wherein the vitreous bond abrasive articleprecursor further comprises at least one of: at least one tortuouscooling channel extending at least partially through the vitreous bondabrasive article precursor; or at least one arcuate cooling channelextending at least partially through the vitreous bond abrasive articleprecursor; and generating, with the manufacturing device by an additivemanufacturing process, the vitreous bond abrasive article precursorbased on the digital object; separating loose powder particles from thevitreous bond abrasive article precursor; and heating the vitreous bondabrasive article precursor to provide the vitreous bond abrasive articlecomprising the abrasive particles retained in a vitreous bond material;and burning out the organic compound.